Diverging dc conductivity due to a flat band in disordered pseudospin-1 Dirac-Weyl fermions

Vigh, Máté and Oroszlány, László and Vajna, Szabolcs and San-Jose, Pablo and Dávid, Gyula and Cserti, József and Dóra, Balázs (2013) Diverging dc conductivity due to a flat band in disordered pseudospin-1 Dirac-Weyl fermions. PHYSICAL REVIEW B CONDENSED MATTER AND MATERIALS PHYSICS (5). pp. 1-5. ISSN 1098-0121

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Abstract

Several lattices, such as the dice or the Lieb lattice, possess Dirac cones and a flat band crossing the Dirac point, whose effective model is the pseudospin-1 Dirac-Weyl equation. We investigate the fate of the flat band in the presence of disorder by focusing on the density of states (DOS) and dc conductivity. While the central hub-site does not reveal the presence of the flat band, the sublattice resolved DOS on the non-central sites exhibits a narrow peak with height 1/pg with g the dimensionless disorder variance. Although the group velocity is zero on the flat band, the dc conductivity diverges as ln(1/g) with decreasing disorder due to interband transitions around the band touching point between the propagating and the flat band. Generalizations to higher pseudospin are given.

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